Fuse



Aug. 4, 1942. c. R. CRAIG v 2,292,058

` FUSE Filed Sept. 17, 1941 )CZ/2J.

lll 5 Inventor: Charles RCr'aigb,

M7? by Js/WM/w His Attorneg.

Patented Aug. 4, 1942 FUSE Charles B. Craig, Pittsiield, Mass., assignerto General Electric Company, a corporation oi New York ApplicationSeptember 17, 1941, Serial No. 411,133

l(c1. zoo-111) Claims.

'My invention relates generally to circuit-interrupting apparatus, suchas secondary fuses, and specifically-is an improvement on the fuseconstruction disclosed and claimed in United States Letters Patent2,172,226, granted September 5, 1939, uponan application of S. R. Smith,and assigned to the same assignee as the present application. Secondaryfuses are usedvery extensively in connection with the distribution ofelectrical energy through overhead secondaries. They are usually used tobridge across insulators, such as `of the strain type, betweentransformer sections. Also, they are often used directly to connectdistribution transformer secondaries to the secondary lines and toisolate service entrance faults.

' -An object of my invention is to provide an improved secondary fusewhich has satisfactory means for indicating when the fuse has blown,which is completely sealed against moisture in the unblown condition toprevent deterioration thereof, which upon interruption of the circuitprevents mechanical separation of the parts thereof, thereby preventingthe dangling of conductors so as to interfere with the operation ofother adjacent sound conductors, or cause secf ondary short circuits toadjacent grounded parts, and which is simple and sturdy in constructionso that, among other things, twisting oi the fuse link in handling orwhen swayed in service by the wind cannot occur.

, A furtherobject of my invention is to provide a new and improvedlow-cost fuse construction particularly suited for but not necessarilylimited tov outdoor installations, such as on overhead secondarydistribution lines.

Further objects and advantages of my invention will become apparent asthe following description proceeds, and the features of novelty7 whichcharacterizemy invention will be pointed cut with particularity intheclaims annexed to and forming a part of this speciiication.

For a better understanding of my invention reference may be had to theaccompanying drawing in which Fig. 1 is a diagrammatic view partly insection of a fuse construction embodying my invention; Fig. 2 is a viewtaken on line 2-.2 of Fig. 1, Figs. 3 and 4 are sectional views somewhatsimilar to' Fig. 1 of modifications of my invention; Fig. 5 is aschematic diagram illustrating the blown condition of a fuse embodyingmy invention, and Figs. 6 and 'l arediagram- :matic showings ofapplications of my invention.

Referring to Fig. 1"oi the drawing, I have illustrated an open-endedtubular casing or cylinder I0 of insulating material f preferablyweatherproof which is adapted to form part oi a housing for a fuse link.Any suitable form of fuse link may be utilized in connection with myinvention and, as shown in Fig. l, the fuse link has a fusible sectionwhich is disposed within cylinder or casing it and is comprised of arelatively low melting point wire Ii and a strain wire i2 connected toand extending between a pair of terminal sleeves I3 and I4. The terminalsleeves i3 and I4 are spaced from one another at their inner adjacentends to provide a gap across which the fusible section is connected. Theouter ends of the terminal sleeves i3 and. il, which are adapted toproject from the opposite ends of the tubular casing lli, are connectedto flexible leads i5 and it, respectively, by crimping or swaging, asindicated at I1, best shown in Fig. 2.

Each of the open ends oi tubular casing i0 through which the outer endsof terminal sleeves i3 and il protrude is preferably closed by a closuremember or stopper i8 formed of a suitable 4 metal and having an openingis therein through which termi; a1 sleeves i3 or il may extend Closuremembers it each have a' cylindrical body portion which nts into the boreof casina i0 and also an outer peripheral flange which has the samediameter as casing Il! and bears against the end thereof. Each closuremember il is also provided with an integral collar portion 20surrounding the opening is through which thev terminal sleeves it or itmay extend, which collar is adapted to be crimped or swaged as indicatedat 2l in Fig. l to the terminal sleeves il or Il,

for a purpose to be described in greater detail hereinafter. Theperipheral flange of the closure or stopper member i8 is provided with aplurality of tabs or lugs 22 which,'in the assembled fuse as shown inFig. 1, iit into cooperating notches 23 formed in the ends of tubularcasing i0, thereby preventing the fuse link from being twisted inhandling or when swayed in service by the wind.

In order to seal the ends of tubular casing I0 against the ventrance ofmoisture, each end is provided with a toroidal packing washer 24 formedof a resilient compressible material and a fiber or other suitablebearing washer 25 annular in shape, both of which are adapted to beslipped over either of the terminal sleeves I3 or I4 so that the packingwasher li'is adjacent closure member I8 and the bearing washer 25 is onthe inner side of toroidal washer 24 relative to casing I0 to serve as abearing member for the compressive force applied to the packing`washer24 to be described hereinafter.

In order to ald in extinguishing the arc formed Y upon rupture of thefusible section II and strain wire I2 of the fuse link, I provide aninner sleeve or cylinder of insulating material 26 which is preferablyformed of a material such as horn ber or the like which emits gas whensubjected to the heat of an electric arc. Inner cylinder or sleeve 26 ispositioned centrally within tubular casing I of Fig. l to enclose thefusible section of the fuse link and is held in this position by a pairof coiled compression springs 21 each fastened to one end thereof. 'Ihecoils at the adjacent ends of springs 21 preferably have such a diameteras closely to encircle the respective ends of inner sleeve 26.Furthermore, the ends of springs 21 which encircle sleeve 26 are eachbent radially inward to form o. locking portion 26 for engagement with acooperating opening 29 in each end of inner sleeve 26. 'I'he outer endsof springs 21 are adapted to bear against bearing washers 26 so thatwhen the fuse device is assembled, packing washers 24 will be compressedto seal the ends of tubular casing I6 in a moisturetight manner. Theround cross section of the toroidal packing washers 24 facilitatesdeformation and radial expansion thereof into sealing engagement withthe terminal sleeves I6 and I4 and the inner wall of tubular casing III.As in the above mentioned Letters Patent, the expanisve force of thepacking washers 24 against the end closures I6 imposes a tension uponthe fuse link and the tensioned fuse link, in turn, maintains thepacking washers under compression. Coil spring means 21 serve tomaintain substantially constant tension on the fusible section of thefuse link regardless of any setting of the packing washers and of anycreeping or straightening out of the strain wire which may occur duringor after final assembly of the fuse device.

In order 'to prevent the terminal sleeves I6 and I4 from being blown outof tubular casing I0 upon interruption of the circuit by rupture offusible element I I thereby to prevent dangling of the conductors I6 andI6 which might swing across other live conductors and cause shortcircuits or the like as well as to prevent hot parts of the apparatusfrom falling to the ground. each of the terminal sleeves I6 and I4 isprovided with an enlarged portion I6a and I4a, respectively. Also, theend turns 21a of coiled compression springs 21, which are remote fromone another when positioned within tubular casing I0, are of a reduceddiameter relative to the remaining turns of these springs so as to slideover terminal sleeves I6 and I4 readily but constructed to engage theenlargements I 6a or- I4a, respectively, upon rupture of the fusibleelement. Upon such rupture of the fusible section of the fuse link, theterminal sleeves I6 and I4 are forced out of tubular casing I0 by thecompressive force of packing washers 24 and springs 21 as well as by theexpulsive forces of the gases formed within inner sleeve 26 whensubjected to the heat of the arc uponrupture of the fusible section ofthe fuse link. However, as soon as the terminal sleeves I6 and I4 havemoved lout of tubular casing I0 to the position indicated in Fig. 5, theend turns 21a of reduced diameter engage the enlargements I3a and I4a ofterminal sleeves I6 and I4, respectively. Since the locking portions 26at the inner ends of springs 21 are hooked in the cooperating openings26 of inner sleeve 26,

electrical separation of terminal sleeves I6 and I4 is permitted butmechanical separation thereof is prevented. Furthermore. the protrusionof one or more of the springs 21 from tubular casing I6 provides anexcellent visual indicating means of the blown condition of the fuserequiring replacement.

In the assembly of the fuse device of Figs. l and 2, the componentelements above described are arranged as illustrated with one of theterminal sleeves crimped to one of the associated flexible cables andwith the corresponding closure member I6 also crimped thereto. Thedesired tension is then applied to the fuse link to maintain the packingmembers 24 under the desired sealing compression and the other terminalsleeve and closure member I6 are crimped or swaged to hold the structurein the manner indicated in Fig. l with the tabs or lugs 22 engaging thenotches 26 in the tubular casing I6 to prevent twisting of the fuselink.

In the fuse device disclosed in Fig. l, it is practically impossible forthe spring means 21 to become unhooked from sleeve 26 to permitmechanical separation of terminal sleeves YI6 and I4 upon blowing of thefuse because of the fact that, in -addition to locking portions 26 beinginserted in openings 26 in sleeve 26, the end turns of coil springs 21closely encircle sleeve 26.

In Fig. 3 I have disclosed a fuse device which is identical in everyrespect with the fuse of Fig. 1 except for the manner in which thecoiled compression springs 21 are attached to inner sleeve 26. Thecorresponding parts of Fig. 3 are designated by the same referencenumerals as in Figs. lA and 2. Instead of the end turns of coiledcompression springs 21 encircling sleeve 26 as in Fig. 1f the ends ofthese springs are bent to form short straight portions 66 parallel tothe spring axis, the ends of which are again bent radially to form thelocking portion 26 as in Fig. l. With this construction, the springs 21can be more readily fastened to sleeve 26. thereby reducing the assemblycost. The operation of the fuse construction in Fig. 3 is in otherrespects identical with that of Fig. 1 and will be readily understood bythose skilled in the art in view of the detailed description includedabove.

In Fig. 4, I have disclosed a fuse device in which only a singlecompression spring is used. and the corresponding parts of Fig. 4 aredesignated by the same reference numerals as in Pigs. l and 3. In thiscase, however, a terminal sleeve 6I is provided in place of the terminalsleeve I6 which is somewhat shorter and which has no enlargement such asI6a thereon. Terminal sleeve 6I is pinned to inner sleeve 26 by pinmeans 62 which engages cooperating openings 66 in inner sleeve 26. Inthis case, if desired, the

single compression spring 21 may be made somewhat longer than thesprings 21 of Figs; 1 and 3 although this is not essential. As in Figs.1 and 3, the packing washers 24 together with compression spring 21provide the tension means for the fuse link, the openings 66 allowingsome longitudinal movement of sleeve 26 with respect to terminal sleeve6I, and the tension of the fuse link holds the resilient packing washersin sealing engagement. The fuse of Fig. 4 is preferably constructed sothat the terminal sleeve I4 including the spring 21 is forced out ofcasing Il upon blowing of the fusible element much more readily than theend of the fuse device which is pinned to the inner sleeve 26.Furthermore, the point of fastening spring 21 to inner sleeve 26 remainswithin the casing in the construction ci Fig. 4 in the same manner as isdisclosed in Fig. 5 so that unhooking ofthe sprlngfrom the sleeve -isprevented. The operation of the fuse device of Fig. 4 Will be obvious tothose skilled in the art and no further discussion thereof will beincluded herewith.

The constructions hereinbefore described provide extremely low-cost fuseunits which may bev `in Figs. 1 to 5 which is diagrammaticallyillustrated and labeled with the casing designation i0.

In Fig. 7 is another typical installation for which the secondary fusesof the type disclosed above are particularly adaptable. In this case,there is shown a transformer 39 supported by a suitable element, such asa wooden pole 40, also supporting secondary powerlines 4l in a wellknownmanner. The transformer 39 is electrically connected to the power linesIl and the live legs of the transformer secondary winding are connectedthrough secondary fuses which are diagrammatically illustrated andlabeled with the casing designation l0.

As Will be evident from the foregoing construction, the fuse devices ofthe present invention are of such weather-tight construction that theymay be installed in yany position without danger of entrance of moistureinto the casing or housing thereof to cause corrosion or damage oftheinternal fuse parts. This fuse, furthermore, is constructed so as topermit electrical but not mechanical separation of the associatedconductors so as not to cause short circuits with other adjacent soundconductors or grounded parts. In addition, this fuse construction hassuitable means for indicating the condition thereof and is simple andsturdy in construction, including, among otherf things, means forpreventing twisting of the fuse link either by handling op when swayedin service by the wind.

While I have shown and described particular embodiments of my invention,it will be obvious to those skilled in the art that various changes andmodifications may be made Without departing from my invention andL'therefore, aim in the appended claims to cover all such changes andmodifications as fall within the true spirit and scope of my invention.

'What I claim as new and desire to secure by Letters Patent of theUnited States, is:

1. In a fuse device, a pair of conductors in spaced relationinterconnected by fusible means,

l an enlargement on one of said conductors, a

protecting means for said fusible means including an outer cylinderof'insulating material, an inner sleeve of insulating material, meansincluding a coiled compression spring having turns of reduced diameterat one end thereof mounted to surround said conductorhaving saidenlargement thereon and operatively connected for imposing tension onsaid fusible means during the unblown condition of said fuse device. andmeans including mechanical connections through said inner sleeveand theother end of said coiled spring so that upon blowing of said fusiblemeans -said turns of reduced diameter engage said enlargement on saidconductor whereby a mechanical but not an electrical connection ismaintained to prevent dangling of said conductors upon operation of saidfuse device.

2. In a fuse'device, a pair of conductors in spaced relationinterconnected by fusible means, an enlargement on one of saidconductors, a protecting means for said fusible means including an outercylinder of insulating material, an inner sleeve of insulating material,means including a coiled compression spring having turns of reduceddiameter at c -e end thereof mounted to surround said conductor havingsaid enlargement thereon and operatively connected for imposing tensionon said fusible means during the unblown condition of said fuse device,means including mechanical connections through said inner sleeve and theother end of said coiled spring so that upon blowing of said fusiblemeans said turns of reduced diameter engage said enlargement of saidconductor to permit electrical but not mechanical separation of saidconductors, and means for preventing said fusible means from beingtwisted.

3. In a fuse device, a pair of conductors in spaced relationinterconnected by fusible means, an enlargement on one of saidconductors, a

- protecting means for said fusible means including an outer cylinder ofinsulating material, an inner sleeve of insulating material, meansincluding a coiled compression spring having turns of reduceddiameter-at one end thereof mounted to surround closely said conductorhaving said enlargement thereon and operatively connected for imposingtension on said fusible means during the unblown condition of said fusedevice, means including a mechanical connection through said innersleeve and the other end of said coiled spring so that upon blowing ofsaid fusible means said turns of reduced diameter engage saidenlargement Vof said conductor to permit electrical but not mechanicalseparation of said conductors, and means for substantially sealing saidouter cylinder against the entrance of moisture during the unblowncondition of said fuse device.

4. In a fuse device, a pair of conductors spaced apart at their inneradjacent ends to provide a i gap, a fusible element bridging said gapand electrically connected at its opposite ends to said conductors, astrain wire connected to and extending between the inner adjacent edgesof said conductors, an enlargement on one of said conductors, aprotecting means for said fusible means including an outer cylinder ofinsulating material, an inner sleeve of insulating material, meansincluding a coiled compression spring having turns of reduced diameterat one end thereof mounted to surround closely said conductor havingsaid enlargement thereon and operatively connected for imposing tensionon said fusible means during the unblown condition of said fuse device,and means including a mechanical connection throughsaid inner sleeve andthe other end of said coiled spring so that upon blowing of said fusiblemeans said turns of reduced diameter engage said enlargement on saidconductor whereby a mechanical but not an electrical connection ismaintained to prevent dangling of said conductors upon operation of saidfuse device.

5. In a fuse device, va pair of conductors in spaced relationinterconnected by fusible means,-

an outer cylinder of insulating material, an inner sleeve of insulatingmaterial. means including a coiled compression spring having turns ofreduced diameter at one end thereof mounted to surround closely saidconductor having said enlargement thereon and operatively connected forimposing tension on said fusible means during the unblown condition ofsaid fuse device, and means including a mechanical connection throughsaid inner sleeve and the other end of said coiled spring so that uponblowing of said fusible means said turns of reduced diameter engage saidenlargement of said conductor to permit electrical but not mechanicalseparation of said conductors, said coiled compression spring beingmaintained in a position where a portion thereof is extended from an endof said outer cylinder when said fusible means has ruptured so as toindicate the blown condition of said fusedevice.

6. A fuse device comprising incombination, a weatherproof tubularcasing, a pair of terminal sleeves interconnected by a fuse link havinga fusible section mounted in said casing with the ends of said terminalsleeves extending outwardly respectively through openings at oppositeends of said casing, means operative normally to tension said fusiblesection and operative upon rupture of said fusible section to effectrelativeI movement apart of said terminal sleeves and widening of thegap between the ruptured ends of said fusible section, and meansincluding said last-mentioned means and an enlargement on one of saidterminal sleeves for permitting electrical separation but preventingmechanical separation of said terminal sleeves to preclude dangling ofthe conductors associated with said fuse device upon rupture of thefusible section in said casing.

7. A fuse device comprising in combination a weatherproof tubularcasing, a fuse link having a fusible section in said casing andconnection portions extending outwardly respectively through openings atopposite ends of the casing, means including a coiled compression springhaving turns of reduced diameter at one end thereof operative normallyto tension said fusible section and operative upon rupture of thefusible section to effect relative movement apart of said connectionportions and widening of the gap between the ruptured ends of thefusible section, and means including said turns of reduced diameter forpermitting electrical but preventing mechanical separation of saidconnection portions upon rupture of said fuse link in said casing.

8. A fuse device comprising in combination a weatherproof tubularcasing, a fuse link having a fusible section in said casing andconnection portions extending outwardly respectively through openings atopposite ends of the casing. means including a coiled compression springhaving turns of reduced diameter at one end thereof operative normallyto tension said fusible section and operative upon rupture of thefusible section to effect relative movement apart of said connectionportions and widening of the gap between the ruptured ends of thefusible section, means including said turns of reduced diameter forpermitting electrical but preventing mechanical separation of saidconnection portions upon rupture of said fuse link in said casing,closure means for substantially moisturproof sealing relationship tosaid openings.

aaoaosa 9. A fuse device comprising in combination. a weatherprooftubular casing. a pair of terminal sleeves interconnected by a fuse linkhaving a fusible section mounted in said casing with the ends of saidterminal sleeves extending outwardly respectively through openings atopposite ends of said casing, means operative normally to tension saidfusible section and operative upon rupture of said fusible section toei'lect relative movement apart of said terminal sleeves and widening ofthe gap between the ruptured ends of said fusible section, meansincluding said last-mentioned means and an enlargement on one of saidterminal sleeves for preventing mechanical separation of said terminalsleeves to prevent dangling of the conductors associated with said fusedevice upon rupture of the fusible section in said casing, closure meansfor the openings in said casing including resilient packing means, andmeans operative under the influence of the tension of said fuse link tomaintain said packing means normally compressed in substantiallymoistureproof sealing relationship to said openings.

10. A fuse device for outdoor installation comprising in combination, aweatherproof tubular casing, a pair of terminal sleeves interconnectedby a fuse link having a fusible section mounted Ain said casing with theends of said terminal sleeves extending outwardly respectively throughopenings at opposite ends of said casing, means operative normally totension said fusible section and operative upon rupture of said fusiblesection to effect relative movement apart of said terminal sleeves Vandwidening of the gap betweenthe ruptured ends of said fusible section,means including said last-mentioned means and an enlargement on one ofsaid terminal sleeves for preventing mechanical separation of saidterminal sleeves to prevent dangling of the conductors associated withsaid fuse device upon rupture of the fusible section in said casing, andmeans for preventing the fuse link from being twisted in handling orwhen swaying in serviceby the wind.

l1. A fuse device for outdoor installation comprising in combination aweatherproof tubular casing, a fuse link having a fusible section insaid casing and connection portions extending outwardly respectivelythrough openings at opposite ends of the casing, means including acoiled compression spring having turns of reduced diameter at one endthereof operative normally to tension said fusible section and operativeupon rupture of the fusible section to effect relative movement apart ofsaid connection portions and widening of the gap between the rupturedends of the fusible section, means including said turns of reduceddiameter for permitting electrical but preventing mechanical separationof said connection portions upon rupture of said fuse link in saidcasing, and means for preventing the fuse link from being twisted inhandling or when swaying in service by the wind.

12. In a fuse device comprising a weatherproof tubular casing, an innersleeve concentrically arranged within said casing and formed of amaterial of a gas-emitting nature when subjected to the heat of anelectric arc, a pair of terminal sleeves interconnected by a fuse linkhaving a fusible section mounted in said casing with the ends of saidterminal sleeves extending outwardly respectively through openings atopposite ends l of said casing, means operative normally to tension saidfusible section and operative upon rupture of said fusible section toeilect relative movement apart of said terminal sleeves and widening ofthe gap between the ruptured endsof said fusible section, and meansincluding said lastmentioned means and an enlargement on one of vsaidterminal sleeves for permitting electrical separation but preventingmechanical separation of said terminal sleeves to preclude dangling ofthe conductors associated with said fuse device upon rupture of thefusible section in said casing.

13. In a fuse device comprising a weatherproof tubular casing, an innersleeve concentrically arranged within said casing and formed of amaterial of a gas-emitting nature when subjected to the heat of anelectric arc, a fuse link having a fusible section mounted in saidsleeve in said casing and connection portions extending outwardlyrespectively through openings at opposite ends of said casing, meansincluding a coiled compression spring having turns of reduced diameterat one end thereof and mechanically connected to said inner sleeve atthe other end thereof operative normally to tension said fusible sectionand operative upon rupture of the fusible section to effect relativemovement apart of said connection portions and widening of the gapbetween the ruptured ends of the fusible section, means including saidturns of reduced diameter for permitting electrical but preventingmechanical separation of said connection portions upon rupture of saidfuse link in said casing, and means for preventing the fuse link frombeing twisted in handling or when swaying in service by the wind.

14. In a fuse device, a pair of conductors in spaced relationinterconnected by fusible means, an enlargement on one of saidconductors, a protecting means for said fusible means including an outercylinder of insulating material, and means adapted to interconnectmechanically said pair of conductors comprising an insulating member anda coiled compression spring hooked to said insulating member and havingturns of reduced diameter at one end thereof mounted to surround closelysaid conductor having said enlargement thereon so that upon blowing ofsaid fusible means said turns of reduced diameter engage saidenlargement on said conductors to permit electrical but not mechanicalseparation of said conductors.

15. In a fuse device, a pair of conductors in spaced relationshipelectrically interconnected by fusible means, an enlargement on one ofsaid conductors, a protecting means for said fusible means including anouter cylinder of insulating material, and means adapted to interconnectmechanically said pair of conductors comprising an insulating member anda coiled compression spring hooked to saidl insulating member and havingturns of reduced diameter at one end thereof mounted to surround closelysaid conductor having said enlargement thereon so that upon blowing ofsaid fusible means said turns of reduced diameter engage saidenlargement on said conductors to permit electrical but not mechanicalseparation of said conductors, said coils of said compression springadjacent said insulating member being closely coiled around saidinsulating member to prevent unhooking of said spring from said member.

CHARLES R. CRAIG.

